Another guy with a messed up Viewsonic VA912b

[BeAuMaN]

Hello.

I went ahead and wrestled with the case on my own VA912b, and got it open. We ordered a replacement, but I thought it'd be nice to have a backup monitor.

I took careful note of the following thread:
https://www.badcaps.net/forum/showthread.php?t=6740

where PCBONEZ suggested the following:

In KF series -> Ripple/ESR:
470uF 25V -> 1200/0.065
470uF 10V -> 580/0.250
22uF 50V -> 135/1.350
100uF 400V -> 950/0.520

Ripple is in mA at 105C and 100KHz -and- ESR is Ohms at 20C and 100KHz.
[Like they are supposed to be.]

If you go to Digikey, out of what they stock, you will need either Chemicon KZE or Panasonic FM to meet or beat those specs.

The 400v may be an exception. There are some series' that only come in higher volts and I dunno all of those off the top of my head. Probably don't need to replace that one anyway.

From what I can tell, all of them are bulging except for the large 100uF 400v and the 22uF 50v. So I'll be ordering those, assuming the above references at still good, or this guide by PlainBill: https://www.badcaps.net/forum/showpo...5&postcount=11

However, my question comes from something else I noticed during my visual inspection...

I included a picture and circled it with red... I apologize for the bad lighting, however I've noticed in other pictures from people with VA912bs, that the orange gunk on top of that square component is smooth...
https://www.badcaps.net/forum/attach...8&d=1237615886
https://www.badcaps.net/forum/attach...2&d=1224960231

... While mine is sort of goopy, almost as if it's removed or somehow used up, and some of it has clumped up on the side (Still inside the square component, but on the side of whatever is in the middle of it).

I'm curious if this is abnormal, or is showing signs of decay. Or if it's something I don't need to be worried about. Also, what is that component called anyway? >,>

Much appreciated.

- Beau

[Wrog]

Re: Another guy with a messed up Viewsonic VA912b

It's a transformer, and is probably completely normal. As for the caps, replace all except the large 400V one unless it has physical signs of failure.

[De3rcr]

Re: Another guy with a messed up Viewsonic VA912b

I have this monitor and it was dead when I got it, replaced all the caps and it has been working for 8 months now. I agree with Wrog replace all but the big one. Make sure you get the right height and diameter.

[BeAuMaN]

Re: Another guy with a messed up Viewsonic VA912b

Question, as I'm generally new to this, reading the guides though...

With PCBONEZ recommended values on Ripple and ESR, if I can't find the exact value, do I go higher or lower on Ripple and ESR? I've been looking at the digikey catalog, and I can't find the exact values...

Thanks!

[PlainBill]

Re: Another guy with a messed up Viewsonic VA912b

Question, as I'm generally new to this, reading the guides though...

With PCBONEZ recommended values on Ripple and ESR, if I can't find the exact value, do I go higher or lower on Ripple and ESR? I've been looking at the digikey catalog, and I can't find the exact values...

Thanks!

You would want to go lower on ESR, higher on ripple.

Note: This is entirely my opinion, supported to a limited extent by measurements and logic.

First of all, ESR and Ripple are 'better than' specifications. As an example, let's take a look at a Panasonic FM capacitor, the EEU-FM1C681. This is a 680uF, 16V capacitor. The tolerance is +-20%, the ESR is .026 ohms, the ripple current is 1.79A, and it's rated for 4000 hours @105°C.

Those specs mean that the capacitor is expected to last at least 4000 hours if operated at 105°C, and with a ripple current below 1.79Amps. During those 4000 hours the capacitance will not drop below 544uF, nor will the ESR rise above .026 ohms. They do not mean it will turn into a blob of goo if it's operated for 4001 hours under those conditions, that it will explode if you increase the ripple current to 1.8Amps, or that the ESR is exactly .026 ohms. That ends the logic part of the discussion.

Now for personal experience. About a year ago I answered an interesting ad in Craigslist. Dave's 2 year old 46" Samsung LCD TV had started performing erratically. The shop told him that that model had bad caps. Since it was out of warranty, it would cost $300 to repair it. Instead, Dave bought a new Sony TV, and wanted to sell the Samsung for $200. I verified the screen was good and gave Dave $200.

Wizard had mentioned that certain lots of Samwah caps are notorious for failing prematurely. These are specific values with certain production dates. When I opened the TV up, sure enough there were half a dozen caps in two different values that had 'popped' their tops. Pulling the caps, their ESR ranged from .5 ohms to several ohms, except for one that read .1 ohm. I check several other caps in the power supply, their ESR reads below .05 ohms and show no signs of bulging.

My next step was to check my inventory. Good, I had enough Nichicon caps to repair the TV. Now I check their ESR by clipping to the ends of the leads. WTF!!! This one reads .06 ohms. Spec is .05!!! Then I get a flash of intelligence and clip to the leads at the body of the cap. .02 ohms, OK, that is better. Checking the rest of the new caps showed their ESR was typically 1/3 to 1/4 of the rated ESR. A quick check of more of the caps in the TV showed the same results. Even after being used for two years, Samwah caps (sometimes referred to as junk by people of low intellect) still read a fraction of their specified ESR.

My conclusion: Buy good quality caps that at least meet the specs of the original. Don't be afraid to replace a cap spec'd at .09 ESR with one speced at .03; odds are the original measured below .03 when it was new. And something gleaned from another stressful encounter, ALWAYS replace the 10 -100 uF caps around the SMPS controller. They will fail without any visible sign.

PlainBill

[BeAuMaN]

Re: Another guy with a messed up Viewsonic VA912b

Thank you Bill. I'll keep this in mind for the caps I order. Hopefully everything will go well once I get everything, which will probably be during winter holidays, since I won't have much work to do around the vineyard.

Thanks again though for your story, I appreciate the experience!